Genetic factors play a major role in the development of epilepsy. With recent advances in human genetics it s now clear that mutations resulting in ion channel dysfunction, neurotransmitter receptor alterations, or abnormal brain development predispose an individual to seizure activity. Although considerable progress has been made in the genetics of seizure susceptibility, virtually nothing is known about mutations that confer seizure resistance. To address this problem, we recently developed an acute seizure model in zebrafish (Danio rerio) e.g., exposure to a common convulsant agent, pentylenetetrazol (PTZ). Using this simple vertebrate model, and pilot funding from an R21 exploratory grant, we completed a large-scale forward-genetic mutagenesis screen to isolate seizure resistant zebrafish mutants. Six seizure resistant zebrafish mutants were identified and confirmed in out-cross testing. Here we propose to continue our study of seizure resistant zebrafish and to identify the underlying gene mutations. Our overall goal is to obtain a better understanding of seizure resistance. A multi-disciplinary strategy is proposed. Techniques include video monitoring and locomotion tracking software to study behavior. Electrophysiological experiments to assess brain function in zebrafish exposed to convulsant agents. Molecular and immunohistochemical studies to monitor immediate early gene expression. Genetic linkage analysis and positional cloning techniques to identify underlying gene mutations in two or three seizure resistant zebrafish mutants. Two specific aims are proposed: (i) To use behavioral, molecular and electrophysiological assays to characterize seizure-resistant phenotypes in zebrafish mutants and (ii) To use molecular analysis to map and clone seizure resistance genes in zebrafish. The results promise to provide new information about the genetics of seizure resistance and may lead to the design of novel anticonvulsant treatments designed to prevent epilepsy.